Re: [Elecraft] Magnetic Loop question

[Bill Leonard N0CU]

"The polarization does not matter to radiation pattern. "

This isn't the case for most antennas we use which launch an electromagnetic
wave by generating an electric field. Ground characteristics affect the
pattern of a vertically polarized wave much more than they affect a
horizontally polarized wave for these types of antennas. The mag loop
however, as I understand it, launches an EM wave by generating a magnetic
field. Do the ground characteristics not affect the pattern of a magnetic
field the way they do an electric field? If they do have the same affect,
then the above statement isn't true.

Bill  N0CU



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Re: [Elecraft] Magnetic Loop question

[Fred Jensen]

Ummm ... there may be a confusion with loops that are electrically large 
... like a circumference of 360 deg.  They are E-field antennas [just 
like a half-wave dipole or 1/4 wave vertical] and the feed point 
determines the polarization.  Polarization matters at VHF and above, but 
at HF, the received polarization will be random and changing due to 
Faraday Rotation in the ionosphere.


I believe this thread is about "small magnetic loops," whose 
circumference  is only a handful of degrees, such as the AlexLoop [a 
resonant transformer], and others directly fed.  The feed point does not 
matter for small magnetic loops.


73,

Fred K6DGW
- Sparks NV DM09dn

- Northern California Contest Club
- CU in the Cal QSO Party 7-8 Oct 2017
- www.cqp.org

On 10/20/2016 4:27 AM, Steven Dick wrote:


The vertical  loop can be horizontally polarized by feeding it in the
middle of the top or bottom edges.
It can be vertically polarized by feeding it in the middle of the
vertical edges.


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Re: [Elecraft] Magnetic Loop question

[John Magliacane via Elecraft]

On Thu, 10/20/16, Steven Dick  wrote:

> The vertical loop can be horizontally polarized by feeding it in the middle 
> of the top or bottom edges.   It can be vertically polarized by feeding it in
> the middle of the vertical edges.

That's true for a loop having a full-wave circumference, but "Magnetic Loops" 
have circumferences that are typically only a fraction of a wavelength, and as 
such operate under a much different mechanism.

A vertically oriented magnetic loop, regardless of where it is fed, will 
achieve the highest degree of coupling to a vertically polarized signal, and 
have a bi-directional (half-wave dipole-like) radiation pattern.

A horizontally oriented magnetic loop, regardless of where it is fed, will 
achieve the highest degree of coupling to a horizontally polarized signal, and 
have an omni-directional radiation pattern.

This is because a magnetic loop is most responsive to the magnetic component of 
the RF wave.

When we speak of RF polarization, we are speaking of the polarization of the 
electric field.  A vertically polarized signal will have a horizontally 
polarized magnetic field, and vice-versa.  It is the horizontally polarized 
magnetic field from a vertically polarized wave front that will cut through the 
center of a vertically oriented magnetic loop and induce a voltage across its 
terminals.


73, de John, KD2BD
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Re: [Elecraft] Magnetic Loop question

[Steven Dick]

On Thu, Oct 20, 2016 at 5:04 AM, Vic Rosenthal  wrote:
> If it is vertically polarized it has a dipole-like pattern, with sharp nulls. 
> If horizontal, it is more or less omnidirectional.
>

This is sort of incorrect.

The polarization does not matter to radiation pattern.

The physical orientation of the loop matters.   If the plane of the
loop is parallel to the ground, it is omnidirectional.

If the loop is vertically oriented, it can be horizontally or
vertically polarized, but in both cases, there is a sharp null in axis
of the loop.
(Technically, if the loop is parallel to the ground, the null points
at the ground and the sky.)
The vertical  loop can be horizontally polarized by feeding it in the
middle of the top or bottom edges.
It can be vertically polarized by feeding it in the middle of the
vertical edges.

Changing the polarization may change elevation angle, and might affect
ground wave propagated signals, but once it bounces, Faraday rotation
makes polarization irrelevant.
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Re: [Elecraft] Magnetic Loop question

[Dave Cole]

On Thu, 2016-10-20 at 12:04 +0300, Vic Rosenthal wrote:
> If it is vertically polarized it has a dipole-like pattern, with sharp
> nulls. If horizontal, it is more or less omnidirectional.
> 
> Vic 4X6GP

Add enough ferrite material to do some decent choking on the feedline,
and the nulls get deeper...  Helps in DFing...

-- 
73's, and thanks,
Dave (NK7Z)
For software/hardware reviews see:
http://www.nk7z.net

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Re: [Elecraft] Magnetic Loop question

[Vic Rosenthal]

If it is vertically polarized it has a dipole-like pattern, with sharp nulls. 
If horizontal, it is more or less omnidirectional.

Vic 4X6GP

> On 20 Oct 2016, at 04:42, Phillip Lontz  wrote:
> 
> Are mag loop antennas very directional?
> Are mag loop antennas a little directional?
> Are mag loops kinda directional?
> So which one?
> Phil
> K5SSR
> 
> What me worry?
> 
>> On Oct 19, 2016, at 9:42 AM, Richard Fjeld  wrote:
>> 
>> This is a follow up to recent post from someone in California who 
>> noticed less output when operating in below freezing temps.
>> 
>> In the thread that followed, I mentioned the relationship of cold to 
>> gain and biasing to prevent
>> thermal runaway.  My last ARRL Handbook is a 2009 edition and 'Thermal 
>> Runaway' can be found
>> in the index.  You may find it interesting.
>> 
>> Dick, n0ce
>> 
>> -- 
>> 
>> 
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Re: [Elecraft] Magnetic Loop question

[Fred Jensen]

On 10/19/2016 6:42 PM, Phillip Lontz wrote:

Are mag loop antennas very directional?


Yes


Are mag loop antennas a little directional?


Yes, more than a little


Are mag loops kinda directional?


The fwd lobe [in the plane of the loop] is very broad, very hard to 
discern the peak, so it really doesn't matter.  The null [orthogonal to 
the plane of the loop] is very sharp, very noticeable.  It can be used 
to null QRN/QRM, provided of course that the QRN/QRM is located in 
exactly that direction.  Fortunately, because the fwd lobe is so broad, 
this actually does work fairly regularly.


K2-AlexLoop


So which one?


See above.  I think I missed the original post [been really busy for a 
retired puke], looks like the thread drifted off the question.


73,

Fred K6DGW
- Sparks NV DM09dn

- Northern California Contest Club
- CU in the Cal QSO Party 7-8 Oct 2017
- www.cqp.org


Phil
K5SSR

What me worry?


On Oct 19, 2016, at 9:42 AM, Richard Fjeld  wrote:

This is a follow up to recent post from someone in California who
noticed less output when operating in below freezing temps.

In the thread that followed, I mentioned the relationship of cold to
gain and biasing to prevent
thermal runaway.  My last ARRL Handbook is a 2009 edition and 'Thermal
Runaway' can be found
in the index.  You may find it interesting.

Dick, n0ce

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Re: [Elecraft] Magnetic Loop question

[W5RDW]

Here is Pixel's info on their loop antenna.

http://www.universal-radio.com/catalog/sw_ant/6142dia.jpg 



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Roger W5RDW
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Re: [Elecraft] Magnetic Loop question

[Charlie T, K3ICH]

Horizontally mounted No
Vertically mounted.Yes, in the plane of the loop (off the ends NOT
perpendicular to the loop.)

Chas
-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of
Phillip Lontz
Sent: Wednesday, October 19, 2016 9:43 PM
Cc: Elecraft Reflector <elecraft@mailman.qth.net>
Subject: [Elecraft] Magnetic Loop question

Are mag loop antennas very directional?
Are mag loop antennas a little directional?
Are mag loops kinda directional?
So which one?
Phil
K5SSR

What me worry?

> On Oct 19, 2016, at 9:42 AM, Richard Fjeld <rpfj...@outlook.com> wrote:
> 
> This is a follow up to recent post from someone in California who 
> noticed less output when operating in below freezing temps.
> 
> In the thread that followed, I mentioned the relationship of cold to 
> gain and biasing to prevent thermal runaway.  My last ARRL Handbook is 
> a 2009 edition and 'Thermal Runaway' can be found in the index.  You 
> may find it interesting.
> 
> Dick, n0ce
> 
> --
> 
> 
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[Elecraft] Magnetic Loop question

[Phillip Lontz]

Are mag loop antennas very directional?
Are mag loop antennas a little directional?
Are mag loops kinda directional?
So which one?
Phil
K5SSR

What me worry?

> On Oct 19, 2016, at 9:42 AM, Richard Fjeld  wrote:
> 
> This is a follow up to recent post from someone in California who 
> noticed less output when operating in below freezing temps.
> 
> In the thread that followed, I mentioned the relationship of cold to 
> gain and biasing to prevent
> thermal runaway.  My last ARRL Handbook is a 2009 edition and 'Thermal 
> Runaway' can be found
> in the index.  You may find it interesting.
> 
> Dick, n0ce
> 
> -- 
> 
> 
> __
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